Electro-hydraulic actuator for prime mover control



R. ROSENCRANZ ENGINE rHRorrLc IN VEN TOR. semag/ ELECTRO-HYDRAULIC ACIUATOR` FOR PRIME MOVER CONTROL Filed June ll, 1965 Aug. 2, 1966 ELECTRIC GOVERNOR CONTROL RESERVOIR United States Patent O M 3,263,694 ELECTRO-HYDRAULIC ACTUATOR FOR PRIME MOVER CONTROL l Robert Rosencranz, Flossmoor, Ill., assignor, by mesne assignments, to Esterline Angus Instrument Company,

Inc., Indianapolis, Ind., a corporation of Delaware Filed June 11, 1963, Ser. No. 287,088 7 Claims. (Cl. 137-36) This invention relates in general to an electro-hydraulic actuator, and more particularly to an electro-hydraulic actuator which is used in :a governor system to precisely cont-rol the speed of a prime power.

Auxiliary electrical power units, as for field or emergency use, often comprise a prime mover, as a Diesel engine, which drives an alternator that supplies electrical power to a load. In many situations it is desirable to operate a plurality of such auxiliary power units in parallel so that they act together in a predetermined manner to supply the load. It is necessary that the generating system be provided with controls over the frequency of the generated energy and over the load division between units. This control must have a fast lresponse to load changes, a high degree of stability and good reliability under field operating conditions. It is also important to provide means for governing the speed of the alternator prime mover which is operatively responsive to the control means. Accordingly, the general purpose of the present invention is to provide precision means for governing the speed of engine driven alternator sets.

`An object 'of the invention is to convert signals received from speed and load sensing devices into mechanical displacements as may be required by the throttle or fuel rack in order to maintain constant engine speed.

Another object of the invention is rto provide an electro-hydraulic actuator for an engine governing system wherein the actuator is adapted to be used with either a Diesel or gasoline engine, both of which require mechanical control of the throttle or fuel lrack for speed regulation.

Still another object of the invention is to provide an electro-hydraulic actuator for an engine governing system wherein the actuator is operative with a relatively small volume of hydraulic fluid under a relatively low pressure.

A further object of the invention is the provision of an actuator as described in the previous paragraphs wherein the actuator output is bi-directional and does not require the use of return springs.

And still another object of the invention is to provide an electro-hydraulic actuator which is simple in .construction, eicient in operation, accurate in the maintenance of constant prime mover speed, well adapted for its intended purposes, and relatively inexpensive to manufacture and maintain.

Further objects and advantages of the invention will be readily apparent from the following specification and the accompanying drawing wherein:

FIGURE 1 is a front elevational view of an electrohydrau-lic actuator embodying the principles of the present invention;

FIGURE 2 is a side elevational view of ythe apparatus shown in FIGURE l with certain parts broken away for clarity; and

FIGURE 3 is a schematic diagram of a system incorporating the apparatus illustrated in FIGURE 1 and FIGURE 2.

While this invention is susceptible to embodiment in many different forms, there is shown in .the drawings and will herein be described in detail one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles 3,263,694 Patented August 2, 1966 ICC o-f the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawin wherein like or corresponding numerals are used to indicate like or oorresponding parts throughout the several. views, a housing 10 in which the actuator components are mounted is shown in FIGURE 1 and FIGURE 2. Housing 10 includes a base 11 having an inlet 12 through which pressurized hydraulic fluid is conveyed to the actuator assemfbly. Inlet 12 communicates with a channel :13 formed in ybase 11, which in turn communicates with a vertical channel f14 in a block-like accumulator 15 that is suitably `secured to base 11 by bolts or the like, not shown. Accumulator 15 serves as a collectionA manifold between inlet 12 and valve 22, to be hereafter described, and includes a pair of longitudinally extending parallel bores 16 and 17. A plate 18 is bolted to one end of accumulator 15 and covers one end of bores 16 and 17, and plugs 19 are press fit in the other ends of the bores 16 and 17 to create two generally fluid-type chambers. Pressure relief means is provided in the form of passages 20 in the sides of accumulator 15 communicating with chambers 16 and 17. A drain 21 is provided in base 11 to convey the exhausted fluid back tothe fluid reser- Voir.

Valve 22 is a four-way single stage servo operated valve similar to that shown in U.S. Patent 2,875,782 to Lee. Valve 22 includes a pair of spaced apart body members 23 and 24, a central rockably mounted flat plate 25, and a pair of spacers 26 and 27. A groove 28 extends laterally through blocks 23 and 24, and spacer 27, and communicates with channel 14.y Longitudinally extending grooves 29 and 30 in blocks 23 and 24 respectively, communicate with lateral groove 28. Vertical bores 31, 31, and 32, 32 extend upwardly from the ends of grooves 29 and 30, respectively, and communicate with lateral bores 33 and 34, which extend from bores 31 through block 23, plate 25, and `block 24. Bore-s 33 and 34 communicate with passages 35, only one of which is shown, that are suitably provided in a, cylinder block 36. Valve 22 and cylinder block 36` are secured to accumulator 15 by bolts or the like, not shown.

Block 36 includes a pair of parallel cylinders 37, each having a piston 38 reciprocally mounted therein. Pistons 38 are formed of a hollow construction as shown at 39 in FIGURE 2, and receive a spring 40 which is biased between piston 38 and a plug 41 which is press lit in sealing fashion in the bottom of each cylinder 37. Block 36 terminates in a pair of spaced apart arms 42 and 43 receiving therebetween a rockably mounted bar 44 having a shaft 46 rigid 'therewith` and suitably journalled in arms 42 and 43 as at 45. Roller bearings 47 are rotatably mounted at the upper ends of pistons 38 and engage the opposed cam like undersurfaces 48 Iof rocker arm 44. Cam surfaces 48 are generated from an involute curve, and thus a resolution of forces is provided which enables. the moment arm of pistons 38 to be constant regardless of fthe angular displacement of rocker arm 44. Therefore the torque output at shaft 46 will be .constant throughout the angular travel of rocker arm 44, and will bear a linear relation to the displacement of pistons 38.

Operation of pistons 38 in cylinders 37 is effected by the rocking of Valve plate 25 which meters pressurized fluid to and from cylinders 37 through ports 33 and 34. The mechanical displacement of valve plate 25 is caused by movement of a flat armature 50 of a torque motor which is connected to valve plate 25 through a vertically adjustable semi-rigid coupling 51. Armature 50 is actuated by a pair of coils 52 and 53 which are so located as to provide differential control of the armature, and which a-re energized by the electronic speed and load sensing means lthat is the subject of co-pending application, Serial No. 144,992, now Patent No. 3,171,966, having the same assignee as the present lapplication.

A differential transformer 55 is bolted to the side of cylinder block 36, and provides the required feed-back electrical signals necessary for the over-all operation of the governing system. Differential transformer 55 includes a movable core 57 fxedly secured to the bearing support pin 58 of a piston roller bearing 47. Thus, all motions of the piston 38 are transferred directly to the differential transforme-r movable core 57 and, since the relationship between the travel of piston 38 and the rotation of the -output shaft 46 is linear, the output of the differential transformer 55 will also bear a linear relationship to the angular displacement of output shaft 46.

The operation of the actuator will be best understood from a consideration of FIGURE 3. Hydraulic uid is drawn from a reservoir 60 by a pump 61 and passes through a suitable filter 62, a pressure relief valve 63 being provided. to limit the overall pressure in the system to a value such as 500 p.s.i. A pressure regulating valve 64 is provided having a range of pressure adjustments such as from to 300 p.s.i. to control the operational pressure of the fluid in the actuator. Pressure regulator valve 64 supplies fluid under the desired pressure to the servo valve 22, which is operated by torque motor 54 in response to-the electrical governor control system set forth in the aforementioned patent application, to meter fluid into cylinders 37 to operate pistons 38. Springs 40 will retain pistons 38 in the normal lposition shown in FIG- URE l and FIGURE 2 in the absence of a signal from the control means. The engine throttle or fuel rack 66 is directly coupled to t-he actuator output shaft 46 and thus the amount of fuel to the prime mover will be regulated by the movement of pistons 38 against the rocker arm 44. It will be understood that either the clockwise or the counterclockwise rotation of shaft 46 may be utilized to increase the supply of fuel to the prime move-r, and that the actuator is thus bi-directional. Also, since pistons 38 operate on opposed sides of the rocker arm pivot, shaft 46 is positively actuated in both the clockwise and counterclockwise directions, and no return springs are necessary. Differential transformer 55 is coupled to a piston 38 to provide the required speed and load signal for the control system 65.

I claim:

1. A actuator for controlling the speed of a prime mover comprising: a housing; a cylinder block mounted in said housing and having a pair of spaced apart parallel cylinders, a rocker arm pivotally mounted on said block and having a cam surface in the form of an involute curve, `the pivot of said arm being spaced equally from said cylinders and said cam surface being positioned in alignment with said cylinders; a rotary four-way flat plate valve mounted in said housing and having discharge ports communicating with said cylinders; means for connecting said valve to a source of fluid; pist-on means actuable by said valve and including a piston reciprocally mounted in each cylinder, spring means urging each piston toward one cylinder end, a roller rotatably positioned at one end of each piston and engaging said ro'cker arm cam surface to pivot said rocker arm upon actuation of said valve; an output shaft on said rocker arm land positioned at a point substantially equally spaced between said cylinders; said shaft being adapted to be connected to the fuel supply of said prime mover to regulate the amount of fuel supplied to said prime mover; and means responsive to the speed of said prime mover for operating said valve.

2. The actuator defined in claim 1 wherein said output shaft is journaled in said block to pivotally mount said rocker arm.

3. The actuator defined in claim 1 wherein a differential transformer is mounted in said housing, said differential transformer having a movable core fxedly secured to one of said pistons and providing a feed-back electrical signal for operation of said actuator.

4. The actuator dened in claim 1 wherein said valve includes a rockably mounted valve plate adapted to meter fluid through said discharge ports, and said means for operating said valve includes a torque motor mounted in said housing and having a movable armature coupled to said valve plate for actuation of the same.

5. An actuator for controlling the speed of a prime mover output comprising: a housing, a cylinder block mounted in said housing and having a pair of cylinders, a rocker arm pivotally mounted on said cylinder block and having a cam surface, a valve mounted in said housing and having discharge ports communicating with said cylinders, means for connecting said valve to a source of fluid, piston means reciprocally mounted in each cylinder and actuable by said valve to engage said rocker arm cam surface and pivot said rocker arm, an output shaft on said rocker arm and adapted to -be coupled to a control for the prime mover output, and means for operating said valve.

6. The actuator defined in claim 5 wherein said valve is a servo operated rotary four-way flat plate valve having a rockably mounted valve plate adapted to meter fluid through said discharge ports.

7. The actuator defined in claim 5 wherein said cam surface is so shaped that said piston means operate through a lever arm which is constant regardless of the angular disposition of said rocker arm.

References Cited by the Examiner UNITED STATES PATENTS 1,859,437 5/1932 Flanders 137-36 X 2,454,565 11/ 1948 Peterson 137-36 3,158,067 1l/1964 Wagner 137-36 X ISADOR WEIL, Primary Examiner.

C. GORDON, Assistant Examiner. 

1. A ACTUATOR FOR CONTROLLING THE SPEED OF A PRIME MOVER COMPRISING: A HOUSING; A CYLINDER BLOCK MOUNTED IN SAID HOUSING AND HAVING A PAIR OF SPACED APART PARALLEL CYLINDERS, A ROCKER ARM PIVOTALLY MOUNTED ON SAID BLOCK AND HAVING A CAM SURFACE IN THE FORM OF AN INVOLUTE CURVE, THE PIVOT OF SAID ARM BEING SPACED EQUALLY FROM SAID CYLINDERS AND SAID CAM SURFACE BEING POSITIONED IN ALIGNMENT WITH SAID CYLINDERS; A ROTARY FOUR-WAY FLAT PLATE VALVE MOUNTED IN SAID HOUSING AND HAVING DISCHARGE PORTS COMMUNICATING WITH SAID CYLINDERS; MEANS FOR CONNECTING SAID VALVE TO A SOURCE OF FLUID; PISTON MEANS ACTUABLE BY SAID VALVE AND INCLUDING A PISTON RECIPROCALLY MOUNTED IN EACH CYLINDER, SPRING MEANS URGING EACH PISTON TOWARD ONE CYLINDER END, A ROLLER ROTATABLY POSITIONED AT ONE END OF EACH PISTON AND ENGAGING SAID ROCKER ARM CAM SURFACE TO PIVOT SAID ROCKER ARM UPON ACTUATION OF SAID VALVE; AN OUTPUT SHAFT ON SAID ROCKER ARM AND POSITIONED AT A POINT SUBSTANTIALLY EQUALLY SPACED BETWEEN SAID CYLINDERS; SAID SHAFT BEING ADAPTED TO BE CONNECTED TO THE FUEL SUPPLY OF SAID PRIME MOVER TO REGULATE THE AMOUNT OF FUEL SUPPLIED TO SAID PRIME MOVER; AND MEANS RESPONSIVE TO THE SPEED OF SAID PRIME MOVER FOR OPERATING SAID VALVE. 